The present invention relates to a wind turbine to convert wind energy into hydraulic energy. Wind energy has long been used as a source of energy in various ways in a small scale, grain milling or water pumping for example, and recently it is reviewed as a form of clean energy, readily available and never exhausted, for large scale utilization such as electric power generation by large sized wind mills.
Wind energy is utilized by converting a part of the kinetic energy of the air passing through wind mills at certain velocity into mechanical energy, i.e. by manifesting itself as the product of the shaft turning force and the angular velocity of the shaft rotation. For the energy conversion in the first stage, as the wind mill for large scale power generation for instance, variable pitch type propellers or vertical Dalius type large sized wind mills are used trying to increase the conversion efficiency as much as possible. For medium and small scale wind mills, however, fixed pitch propeller type wind mills are generally used, and in this case, it is desired to use the mechanical energy produced more effectively since the energy conversion efficiency is substantially lower as compared with the large sized wind mills. From this viewpoint, it was attempted to drive a hydraulic pump by wind mills to pressurize the oil, and to cause pressure loss positively to the hydraulic oil by passing the pressurized hydraulic oil through the orifice or throttle valve assembled in series into the hydraulic circuit. To convert wind energy into hydraulic energy and further into heat energy and to use the heat energy for example, for heating would be one of the best ways of utilizing the mechanical energy of medium and small scale wind mills, because a considerable portion of the friction loss, (including fluid friction) in the energy conversion process, i.e. the heat energy loss can be collected in the form of temperature rise of oil. This technology is disclosed in the Specification of U.S. Pat. No. 3,989,189.
As this type of equipment is ordinarily operated continuously over a long period, it is important that no troubles develop during the period and that not much care is required for the maintenance. Since the hydraulic oil is used by circulation, the heat evolved in the later conversion process into heat energy may possibly affect the former conversion process of wind energy into hydraulic energy thus overheating the system. It is essential, therefore, to keep the oil temperature at a constant level, for instance, to prevent the temperature from going up above 80.degree. C. as it leads to troublesome maintenance such as replacement or repair if the oil deteriorates or the sealing materials and bearings are damaged by excessive temperature rise of the system when the heat energy obtained from wind energy and the consumption are unbalanced resulting in the accumulation of extra heat energy in the heat generation system. To the wind mills used as the means to introduce wind energy, it is also necessary to prevent damage due to over-speed rotation when a high wind continues for a long time.